Internal combustion engines convert chemical energy in a fuel to mechanical energy. As part of the conversion, the fuel can be combusted, thus causing hot combustion products to expand within the engine. The expansion of the combustion products can be used to move mechanical components of the engine, such as pistons. Combustion reactions can have several products, or emissions, some of which can be undesirable. For example, when hydrocarbons are used as fuel, combustion products can include HC, CO, CO2 and NOx. 
In an attempt to reduce emissions, efforts have been made to utilize substantially carbon-free hydrogen as a combustion fuel instead of hydrocarbons. When hydrogen (H2) is used as the fuel, there is not a substantial amount of HC, CO, or CO2 emissions, because the fuel does not include carbon that can be turned into HC, CO, or CO2. Therefore, hydrogen fuel is currently viewed as a good fuel choice for environmentally clean engines.
The inventor herein has recognized that it can be difficult to achieve a desired air-to-fuel ratio when hydrogen is used as a combustion fuel. In particular, it can be difficult to introduce enough air into the cylinder relative to the amount of fuel in the cylinder. Unlike more conventional liquid fuels, hydrogen gas can occupy a significant volume within a cylinder, thus limiting the volume available for air at a given pressure.
Others have attempted to address this problem by using direct cylinder fuel injection so that a full charge of air can be introduced to a cylinder and effectively trapped within the cylinder before hydrogen is injected. In this manner, the cylinder contains a full charge of air, and the injected hydrogen simply increases the pressure within the cylinder. Thus far, direct hydrogen fuel injectors have evolved from existing injectors designed to inject other fuels, such as natural gas or propane.
The inventor herein has recognized that the design and material selection for various components in such direct hydrogen fuel injectors are inadequate for hydrogen fuel applications. Using such injectors, internal failures such as seizing, galling, and leakage can cause rough running and misfiring in as little as five hours of operation.
At least some of the issues associated with direct hydrogen fuel injection may be addressed by a fuel injector including a fuel channel configured to receive pressurized gaseous fuel from a fuel rail, a nozzle in fluid communication with the fuel channel, and including tapered portions configured to be seated adjacent a cylinder head, a pintle having an opened position and a closed position, wherein pressurized gaseous fuel is introduced from the nozzle directly into a combustion chamber when the pintle is in the opened position and wherein introduction of the pressurized gaseous fuel is substantially blocked when the pintle is in the closed position, and a pintle controller configured to selectively move the pintle between the closed position and the opened position. In this manner, the fuel injector may be at least partially shielded from the heat of the combustion reaction.
At least some of the issues associated with direct hydrogen fuel injection may be addressed by a fuel injector that includes a gas dampener including a first portion that moves with the pintle and a second portion that is fixed relative the nozzle, wherein a gas cushion exists between the first and second portions when the pintle is in the opened position, and wherein the gas cushion at least partially limits the first portion and the second portion moving toward one another, thereby at least partially slowing the pintle as it moves from the opened position to the closed position. In this manner, the fuel injector life may be improved by decreasing the force with which the pintle closes.
At least some of the issues associated with direct hydrogen fuel injection may be addressed by a fuel injector that includes a gas bearing assembly configured to align the pintle relative the nozzle. A gas bearing assembly may have a longer effective lifetime than another type of bearing arrangement when operating with a less lubricating gaseous fuel.
At least some of the issues associated with direct hydrogen fuel injection may be addressed by a fuel injector that includes a bearing mechanism located proximate the nozzle and configured to align the pintle relative the nozzle. The proximity of the bearing arrangement to the nozzle opening may help create a better seal than if only a bearing arrangement located distal the nozzle is used.